feat(environments): env CRUD, workspace switcher, CLI + MCP parity (#68)

Environment lanes existed as seeded rows (production/preview/development)
with a per-service environment label, but there was no way to list,
create, or delete them. Adds the management surface and the switcher:

- GET /projects/:id/environments with live service counts (sqlc)
- POST /projects/:id/environments — lowercase dns-label names, 1-50
  chars, unique per project (409 on dupe)
- DELETE /environments/:id — refuses while it holds services (409)
- Workspace service list gains env filter chips with counts plus an
  inline "+ env" creator
- CLI: containr environments list|create|delete (--yes on delete);
  MCP: containr_environments_list/create/delete (delete needs confirm)
- OpenAPI: new Environments tag + ProjectEnvironment schema

Live-verified: list counts, name validation, dupe 409, empty delete,
non-empty 409, CLI list.

Generated with [Devin](https://devin.ai)

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

ROADMAP2.md

@@ -523,7 +523,11 @@ and wired refs, one click or one CLI call.
 - [x] **Preview environments runtime** — previews are real service clones:
   branch override, queued deployment, node-domain hostnames, TTL sweeper,
   promote = redeploy of the source at the preview branch.
-- [ ] **Environments** — env switcher, per-env vars/domains, promote.
+- [x] **Environments** — CRUD (`GET/POST /projects/:id/environments`,
+  `DELETE /environments/:id`), switcher chips with service counts in the
+  workspace, CLI `environments` + MCP parity. Per-env vars/domains ride the
+  service's own scope (one env per service); promote ships via preview
+  promote.
 - [ ] **sqlc port** — ~140 raw `database/sql` sites → `sqlc/queries/`.
 - [ ] **Tests** — canvas/wizard frontend coverage, deployment/template/
   webhook table tests, Playwright e2e golden path.